This invention concerns archery devices such as archery bows and crossbows in which the tips of flexibly bendable limbs are connected by a drawstring. Upon drawing of the drawstring with a projectile such as an arrow or bolt nocked to the midpoint, stored potential energy is generated, which is transferred to the arrow at firing to launch it into flight.
Maximum effort required is at full draw, limiting the stiffness of the bow able to be aimed accurately by an archer.
There has heretofore been developed so called "compound bows" using rotary elements or reels. These rotary elements, commonly called "cams" when they are non-circular and "wheels" when they are circular but mounted off-center, are used to reduce the effort required to hold the midpoint of the drawstring at full draw, and better aiming is possible from this reduction in effort. Such an archery bow is described by Allen, U.S. Pat. No. 3,486,495.
In Butler, U.S. Pat. No. 4,201,182, there is disclosed pivoting flexible limbs which are attached to a rigid handle. However, this arrangement still uses separate variable leverage devices, i.e., bell cranks to reduce the maximum effort required.
Another such arrangement is shown in U.S. Pat. No. 4,287,867 to Islas.
The span of a bow is determined to a large extent by the need to roughly match the draw distance able to be executed by the archer to the drawstring slack developed in bending the limbs to full draw. Such need results in a substantial span dimension for bows to prevent excessive limb bending and also finger pinching due to a too acute angle between the segments of the drawstring.
The Allen design and others using rotary elements do provide bowstring slack by unwinding of drawstring from the rotary elements to alleviate the above problem, but, as noted, this requires the separate rotary elements.
Accordingly, it is an object of the present invention to provide an archery device in which a reduction in drawstring resistance at maximum draw is achieved without the use of separate variable leverage devices.
It is a further object of the present invention to provide an archery device in which the span of the limb tips may be reduced without excessive limb bending or finger pinching, generating drawstring slack by an effect other than pure bending of the limbs and/or drawstring payout from rotary elements or other devices.